Cooling system for electronic equipment

ABSTRACT

In a cooling system for an electronic device of the present invention, server rooms in which a plurality of servers are placed, an evaporator which is provided close to each of the servers, and cools exhaust air from the server by vaporizing a refrigerant with heat generating from the server, a cooling tower which is provided at a place higher than the evaporator, cools the refrigerant by outside air and water sprinkling, and condenses the vaporized refrigerant, and a circulation line in which the refrigerant naturally circulates between the evaporator and the cooling tower. According to the cooling system, an electronic device which is required to perform a precise operation with a heat generation amount from itself being large, such as a computer and a server, can be efficiently cooled at low running cost.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of commonly owned, co-pending U.S.patent application Ser. No. 12/945,345, filed Nov. 12, 2010 and U.S.Pat. No. 7,855,890, issued Dec. 21, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cooling system for an electronicdevice, and particularly, to a cooling system for an electronic devicefor efficiently cooling an electronic device which is required toperform a precise operation with a heat generation amount from itselfbeing large, such as a computer and a server.

2. Description of the Related Art

In recent years, with improvement in the information processingtechnique and development of the Internet environments, the informationprocessing amount which is required has increased, and data processingcenters for processing various kinds of information in large volume arein the spotlights as business. For example, in the server room of thedata processing center, a number of electronic devices such as computersand servers are installed in the concentrated state, and arecontinuously operated night and day. Generally, for installation ofelectronic devices in a server room, a rack mount method is a mainstream. The rack mount method is the method for stacking racks(casings), which house electronic devices by dividing the electronicdevices according to the functional unit, on a cabinet in layer. Anumber of such cabinets are arranged and disposed on the floor of aserver room. These electronic devices which process information rapidlyhave improved in processing speed and processing capability, and theheat generation amount from the electronic devices continues toincrease.

Meanwhile, these electronic devices require a constant temperatureenvironment for operation, and the temperature environment for normaloperation is set to be relatively low. Therefore, when the electronicdevices are placed in a high-temperature state, they cause troubles suchas system stops. Consequently, the fact is that the air-conditioningpower which operates the air-conditioning machines for cooling theinsides of the server rooms is significantly increased. Thus, reductionin the air-conditioning power becomes urgently necessary not only fromthe viewpoint of cost reduction in business management but also from theviewpoint of conservation of the global environment.

From such a background, the techniques for efficiently coolingelectronic devices are proposed as seen in National Publication ofInternational Patent Application No. 2006-507676, and Japanese PatentApplication Laid-Open No. 2004-232927. National Publication ofInternational Patent Application No. 2006-507676 proposes that a flowpath for chilled air to flow in a closed loop via an electronic deviceis formed by mounting the electronic device with a back cover, a frontcover and a side-mounted chilled air sub-frame, and providing a fan anda heat exchanger in the chilled air sub-frame.

Further, Japanese Patent Application Laid-Open No. 2004-232927 proposesthat in an air-conditioning system for a computer room equipped with arack group for storing electronic devices, which is internally mountedwith an evaporator and a fan, the cooling air led from outside the roomis caused to flow in an internal space under the floor to cool theelectronic devices stored in the rack for storing electronic devices,through an evaporator, cools a condenser which is mounted on the rearsurface of the rack for storing electronic devices, flows in a space ata rear surface or above the rack for storing electronic devices, and isdischarged outdoor via a ventilator. Further, Japanese PatentApplication Laid-Open No. 2007-127315 is not the invention relating tocooling of electronic devices, but introduces the art of naturallycirculating a refrigerant between the evaporator and the condenser.

SUMMARY OF THE INVENTION

Incidentally, in the conventional cooling system for an electronicdevice, electronic devices are cooled by not only cooling by anair-conditioning machine, but also by using a cooling devices directlyattached to the electronic devices in combination, and thereby, theeffect of reducing the air-conditioning power of the air-conditioningmachine can be expected.

However, the operation power for the cooling device which is directlyattached to the electronic device is added, though the air-conditioningpower is reduced, and therefore, the conventional cooling system cannotbe said sufficient yet from the viewpoint of total energy saving.Accordingly, reduction in running cost by additional energy saving isrequired. Above all, energy saving in the respect of cooling by directlyattaching the cooling device to the electronic device is desired.

The present invention is made in view of such circumstances, and has anobject to provide a cooling system for an electronic device capable ofefficiently cooling an electronic device which is required to perform aprecise operation with an amount of heat generation from itself beinglarge, such as a computer and a server, at low running cost.

In order to attain the above described object, a first aspect of thepresent invention provides a cooling system for an electronic devicecharacterized by comprising a device room in which a plurality ofelectronic devices are placed, an evaporator which is provided close toeach of the electronic devices, and cools exhaust air from theelectronic device by vaporizing a refrigerant with heat generating fromthe electronic device, a cooling tower which is provided at a placehigher than the evaporator, cools the refrigerant by outside air andwater sprinkling, and condenses the vaporized refrigerant, and acirculation line in which the refrigerant naturally circulates betweenthe evaporator and the cooling tower.

The present inventor paid attention to the fact that the heat generationamount from the electronic devices a plurality of which are placed in adevice room has abruptly increased in recent years, and heat at a hightemperature (high-temperature air) generates from the electronicdevices. The present inventor has obtained the knowledge that thecirculation line which naturally circulates the refrigerant between theevaporators provided close to the electronic devices and the coolingtowers provided at the places higher than the evaporators and coolingthe refrigerant with the outside air and water sprinkling for a longperiod throughout a year without needing a condenser (supplied with coldwater from a refrigerator) and a compressor.

More specifically, according to the first aspect, the transportationpower for transporting the vaporized refrigerant gas to the coolingtower installed at the place higher than the evaporator by promotingevaporation of the refrigerant by directly exchanging thehigh-temperature heat generated (discharged) from the electronic device(usually having the fan which takes in the air of the device room anddischarges the air) in the high temperature state with the refrigerantflowing in the evaporator. Further, the refrigerant gas vaporized in theevaporator has a high temperature, and thereby, the cooling capacity forcondensing the vaporized refrigerant gas and making the refrigerant gasa refrigerant liquid can be made small. Accordingly, instead of thecondenser (supplied with cold water from the refrigerator), the coolingtower which cools the refrigerant with the outside air and watersprinkling can be used. The refrigerant liquid which is cooled andcondensed flows down to the evaporator located downward from the coolingtower, and thereby, the circulation line in which the refrigerantnaturally circulates between the evaporator and the cooling tower can beconstructed.

By constructing the natural circulation line like this, thetransportation power cost of the refrigerant is made unnecessary, and byusing the cooling tower which cools the refrigerant with the outside airand the water sprinkling at the cooling side of the circulation line,the heat source load for cooling can be remarkably reduced, and therunning cost for cooling the refrigerant can be significantly reduced.

A second aspect of the present invention is, in the first aspect,characterized by further comprising a heat exchanger which cools therefrigerant, a parallel line which is a flow path for the refrigerant,connected to the circulation line, and is provided so that the heatexchanger has parallel relation with respect to the cooling tower, and aparallel control mechanism which controls a refrigerant amount of therefrigerant which is fed to the parallel line from the circulation line.

The second aspect defines the control of the refrigerant which is fed tothe cooling tower and the heat exchanger when the heat exchanger isdisposed so as to have parallel relation with respect to the coolingtower.

According to the second aspect, as the device for cooling therefrigerant, in addition to the cooling tower, the heat exchanger whichcools the refrigerant is connected parallel with the circulation lineand constituted to have parallel relation with the cooling tower tocontrol the refrigerant amount, which is fed to the heat exchanger, withthe parallel control mechanism. Thereby, the cooling tower and the heatexchanger can be efficiently used so that the running cost becomes theminimum in accordance with the cold heat load necessary for condensingthe refrigerant gas vaporized in the evaporator.

A third aspect of the present invention is, in the second aspect,characterized in that the parallel control mechanism comprises anoutside air temperature sensor which measures outside temperature, aparallel valve which is provided in the parallel line, and regulates anamount of the refrigerant which is refrigerant gas returning from theevaporator and flowing into the heat exchanger, and a parallel controlpart which calculates capacity of cooling the refrigerant in the coolingtower from a measurement result of the outside air temperature sensor,and regulates an opening degree amount of the parallel valve from aresult of the calculation to control a refrigerant amount which is fedto the heat exchanger.

The cooling capacity of the cooling tower significantly depends on theoutside air temperature. Accordingly, by constituting the system as inthe third aspect, a part of the refrigerant flowing in the circulationline can be made to flow into the heat exchanger automatically inaccordance with the variation in the outside air temperature, andtherefore, only insufficiency of the cooling capacity of the coolingtower is supplied by the heat exchanger. Thereby, the running cost canbe further reduced.

In short, in order that the cooling tower can effectively use theoutside air temperature, the operator of the cooling system sets thesummer season, the intermediate season and the winter season. Here,generally, the summer season is set to be June to July, the springseason as the intermediate season is set to be March to May, the autumnseason as the intermediate season is set to be September to November,and the winter season is set to be December to February, but small shiftto before and after these settings does not matter.

A fourth aspect of the present invention is, in the second aspect,characterized in that the parallel control mechanism comprises a coolingtower outlet port sensor which measures refrigerant temperature and/orrefrigerant pressure at an outlet port of the cooling tower, a parallelvalve which is provided in the parallel line and regulates an amount ofthe refrigerant which is refrigerant gas returning from the evaporatorand flowing into the heat exchanger, and a parallel control part whichregulates an opening degree amount of the parallel valve so that ameasurement result of the cooling tower outlet port sensor becomes apredetermined value to control a refrigerant amount which is fed to theheat exchanger.

The fourth aspect is another mode of the parallel control mechanism, andby measuring the refrigerant temperature or the refrigerant pressure ofthe cooling tower outlet port sensor provided at the cooling toweroutlet port, the cooling capacity which the cooling tower has at thepoint of time of measurement can be grasped. Accordingly, the openingdegree amount of the parallel valve is regulated based on themeasurement result, and a part of the refrigerant flowing in thecirculation line can be made to flow into the heat exchangerautomatically. Therefore, only insufficiency of the cooling capacity ofthe cooling tower is supplied by the heat exchanger. Thereby, therunning cost can be further reduced.

A fifth aspect of the present invention is, in the first aspect,characterized by further comprising a heat exchanger which cools therefrigerant, a series line which is a flow path for the refrigerant,connected to the circulation line, and is provided so that the heatexchanger has series relation with respect to the cooling tower, withthe line being constituted so that the refrigerant returning from theevaporator reaches the heat exchanger after passing through the coolingtower, and a series control mechanism which controls cooling capacity ofthe heat exchanger.

The fifth aspect defines the control of the refrigerant which is fed tothe cooling tower and the heat exchanger when the heat exchanger isdisposed to have the series relation with respect to the cooling tower.

According to the fifth aspect, the refrigerant gas which returns fromthe evaporator is first cooled in the cooling tower, and next flows intothe heat exchanger, and the series control mechanism which controls thecooling capacity of the heat exchanger is provided. Therefore, onlyinsufficiency of the cooling capacity in the cooling tower can besupplied by the heat exchanger. Thereby, the cooling tower and the heatexchanger can be efficiently used so that the running cost becomes theminimum in accordance with the cold heat load necessary for condensingthe refrigerant gas vaporized in the evaporator. As a result, therunning cost can be further reduced.

A sixth aspect of the present invention is, in the fifth aspect,characterized in that the series control mechanism comprises a heatexchanger outlet port sensor which measures a refrigerant temperatureand/or refrigerant pressure in the heat exchanger outlet port, a primaryrefrigerant valve which regulates a refrigerant amount of a primaryrefrigerant for cooling the refrigerant flowing into the heat exchanger,and a series control part which controls the primary refrigerant valvebased on a measurement result of the heat exchanger outlet port sensor,and the series control part controls the primary refrigerant valve sothat the measurement result of the heat exchanger outlet port sensorbecomes a predetermined value.

Here, the predetermined value refers to the temperature or the pressurenecessary for the refrigerant to circulate naturally in the circulationline.

According to the sixth aspect, by conducting control so that themeasurement result of the heat exchanger outlet port sensor becomes apredetermined value, the heat amount of the primary refrigerant can becontrolled so that only insufficiency of the cooling capacity of thecooling tower is supplied in the heat exchanger when the refrigerantsequentially flows into the heat exchanger from the cooling tower.Accordingly, useless cooling energy is not required in the heatexchanger.

Thereby, the temperature of the outside air which is the cold heatsource of the cooling tower can be effectively used irrespective of thesummer season, intermediate season, or winter season, and therefore, therunning cost can be further reduced.

A seventh aspect of the present invention is, in the fifth or sixthaspect, is characterized in that the series control mechanism comprisesa cooling tower outlet port sensor which measures refrigeranttemperature and/or refrigerant pressure at the cooling tower outletport, a bypass line which can feed refrigerant gas returning from theevaporator into the heat exchanger, a bypass valve which regulates aflow rate of refrigerant gas flowing in the bypass line, a regulatingvalve provided at the cooling tower outlet port, and a series controlpart which controls the bypass valve and the regulating valve based on ameasurement result of the cooling tower outlet port sensor, and theseries control part controls the bypass valve and the regulating valveso that the measurement result of the cooling tower outlet port sensorbecomes a predetermined value.

Here, the predetermined value refers to the temperature or the pressurenecessary for the refrigerant to circulate naturally in the circulationline.

According to the seventh aspect, for example, in the summer season whenthe outside air temperature rises, and the cooling capacity of thecooling tower reduces, if all the amount of refrigerant gas returningfrom the evaporator passes through the cooling tower, all the amount ofthe refrigerant gas cannot be cooled to the temperature and pressurewhich are necessary for the refrigerant to circulate naturally, and thecooling capacity of the cooling tower which is usable cannot besufficiently used. However, by operating the bypass valve and theregulating valve so that the measurement result of the cooling toweroutlet port sensor becomes a predetermined value, the flow rate of therefrigerant gas which flows into the cooling tower is controlled, andthe refrigerant at a predetermined temperature and pressure can beobtained at the cooling tower outlet port. Accordingly, useless coolingenergy is not needed in the heat exchanger.

Thereby, the temperature of the outside air which is the cold heatsource of the cooling tower can be effectively used irrespective of thesummer season, intermediate season, or winter season, and therefore, therunning cost can be further reduced.

An eighth aspect of the present invention is, in the sixth or seventhaspect, characterized in that the series control mechanism furthercomprises an outside air temperature sensor which measures outside airtemperature, a bypass line which can feed the refrigerant gas returningfrom the evaporator into the heat exchanger, and a bypass valve whichregulates the flow rate of the refrigerant gas which flows in the bypassline, and the series control part totally closes the regulating valveand totally opens the bypass valve to shut off return of the refrigerantgas to the cooling tower to guide all the refrigerant gas to the heatexchanger, when the measurement result of the outside air temperaturesensor reaches a predetermined value or more.

In the eighth aspect, control is conducted by incorporating the outsideair temperature into the constitution of the series control mechanism ofthe sixth or seventh aspect. More specifically, for example, in thesummer season when the outside air temperature becomes high and thecooling capacity of the cooling tower reduces the most, the coolingeffect of the refrigerant sometimes can be hardly obtained even if thecooling tower is used. At this time, use of both the cooling tower andthe heat exchanger becomes a problem from the viewpoint of the runningcost. Accordingly, the outside temperature which causes such a problemis grasped in advance, and when the outside air temperature sensor whichmeasures the outside air temperature indicates a predetermined value ormore (grasped temperature or more), the regulating valve and the bypassvalve are controlled to shut off the flow of the refrigerant gasreturning to the cooling tower from the evaporator so that all therefrigerant gas flows into the heat exchanger. Thereby, the runningcost, for example, in the summer season when the cooling capacity of thecooling tower reduces the most can be further reduced.

A ninth aspect of the present invention is, in any one of the first toeighth aspects, characterized by further comprising an air-conditioningmachine which cools high-temperature air taken in from the device room,and returns the air into the device room, and an air-conditioningcirculation line which is branched from the circulation line, andcirculates the refrigerant to and from a cooling part of theair-conditioning machine.

According to the ninth aspect, the refrigerant in the circulation linewith the running cost for cooling the refrigerant being low is also usedas the cold heat source of the air-conditioning machine for cooling theinside of the electronic device room with cold air. Thereby, the runningcost for operating the air-conditioning machine can be also reduced.

Further, by using the air-conditioning machine and the evaporator forcooling an electronic device in combination, generation of heataccumulation (local high-temperature regions) in the server room can besuppressed, and the temperature of the supply air from theair-conditioning machine which air-conditions the entire room can beraised in temperature, as compared with the conventionalair-conditioning system (the method for performing air-conditioning bycirculating the air in the entire electronic device room byair-conditioning with air blown from the floor disclosed in JapanesePatent Application Laid-Open No. 2004-232927). Thereby, in the presentinvention, higher vaporization (evaporation) temperature of therefrigerant can be adopted as compared with the conventional system, andthe capacity of the cooling tower can be sufficiently used. Accordingly,supplying the refrigerant in the circulation line to the cooling part ofthe air-conditioning machine contributes to both energy saving of theair-conditioning machine and exhibition of the capacity of the coolingtower.

A tenth aspect of the present invention is, in the ninth aspect, ischaracterized in that the plurality of electronic devices are dividedinto a plurality of groups, heat exchangers for groups are providedhalfway through the circulation line by the number of groups into whichthe electronic devices are divided, the circulation line is constitutedof a main circulation line in which the refrigerant circulates betweenthe cooling tower and/or the heat exchanger and the heat exchangers fora group, and a group circulation line in which the refrigerantcirculates between the heat exchangers for groups and the evaporatorand/or the cooling part of the air-conditioning machine.

According to the tenth aspect, via the heat exchanger for a groupprovided at each of the groups into which the electronic devices aredivided, the circulation line is constituted of a main circulation linein which the refrigerant circulates between the cooling tower and/or theheat exchanger and the heat exchanger for a group, and a groupcirculation line in which the refrigerant circulates between the heatexchanger for a group and the evaporator and/or the cooling part of theair-conditioning machine, whereby the operation of the groups can beedge-cut from each other.

Thereby, if abnormality occurs to, for example, the evaporator of onegroup, or the flow of the refrigerant stops, the abnormality does notaffect the other group. Accordingly, occurrence of abnormality to thecooling of all the electronic devices placed in the device rooms can beprevented.

The refrigerants which flow in the main circulation line and the groupcirculation line may be of the same kind or may be of different kinds.

A eleventh aspect of the present invention is, in any one of claims 1 to10, characterized by further comprising a flow rate regulating devicewhich is provided in a refrigerant gas flow path at a position of theevaporator outlet port of the circulation line, and regulates arefrigerant flow rate, a temperature sensor which detects temperature ofair discharged from the evaporator, and a controller which controls theflow rate regulating device, and characterized in that the controllercontrols the flow rate regulating device so that the temperature sensorbecomes a predetermined value.

According to the eleventh aspect, by controlling the refrigerant flowrate in the refrigerant gas flow path at the evaporator outlet portside, the vaporization (evaporation) temperature of the refrigerant andthe refrigerant operation temperature can be made higher as comparedwith the case of controlling the refrigerant flow rate at therefrigerant liquid flow path side as in the conventional system.Thereby, operation of the vaporization (evaporation) temperature toshift to the high temperature side can be made. Thus, the refrigerantoperation temperature is made high, and the heat source temperature canbe made high. Accordingly, prevention of reduction in vaporization(evaporation) temperature can be achieved, and therefore, thiscontributes to prevention of condensation formed in the evaporator.

A twelfth aspect of the present invention is, in any one of the first toeleventh aspects, characterized in that the electronic device is aserver, and the device room is a server room.

The present invention can be applied to all the electronic devices whichare required to perform precise operations, with a heat generationamount from themselves being large, but a larger effect can be expected,when the electronic device is a server and the device room is a serverroom.

As described above, according to the cooling system for an electronicdevice according to the present invention, an electronic device which isrequired to perform a precise operation, with a heat generation amountfrom itself being large, such as a computer and a server, can beefficiently cooled at low running cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view explaining a first embodiment of a coolingsystem for an electronic device of the present invention;

FIG. 2 is an explanatory view explaining a server and a server rack;

FIG. 3 is a conceptual view explaining a second embodiment of thecooling system for an electronic device of the present invention;

FIG. 4 is a conceptual view explaining a third embodiment of the coolingsystem for an electronic device of the present invention; and

FIG. 5 is a conceptual view explaining a fourth embodiment of thecooling system for an electronic device of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a cooling system for an electronic deviceaccording to the present invention will now be described in detail inaccordance with the accompanying drawings. As one example of anelectronic device, an example of a server placed in a server room willbe described.

First Embodiment

FIG. 1 is a conceptual view showing a cooling system 10 for anelectronic device of a first embodiment of the present invention.

As shown in FIG. 1, in a two-storied building 12, server rooms 14A and14B are formed in a first floor and a second floor respectively.Underfloor chambers 22A and 22B are respectively formed on the backsides of floor surfaces 20A and 20B on the first floor and the secondfloor. A plurality of air outlet ports (not illustrated) are disposed inthe floor surfaces 20A and 20B. Cold air from air-conditioning machines78 (see FIG. 3) which will be described later is blown into the serverrooms 14A and 14B from the floor surfaces 20A and 20B through theunderfloor chambers 22A and 22B. The air outlet ports are preferablydisposed in the vicinity of the front surface side of each of servers28, and the cold air blown from them is supplied to the servers 28,whereby the servers 28 can be efficiently cooled.

As shown in FIG. 2, server racks 26 are placed in the server rooms 14Aand 14B, and a plurality of severs 28 are stored in the server racks 26in the state stacked in layer. The server rack 26 is preferably disposedto be movable by being provided with moving casters 24. The server 28 isequipped with a fan 30, and by taking in the air of the server rooms 14Aand 14B and discharging the air as shown by the arrow 32, the heat whichgenerates in the server 28 is discharged from the server 28. Thetwo-storied building 12 shown in FIG. 1, the numbers of the server rooms14A and 14B, the number of the server racks 26 placed in the serverrooms 14A and 14B, the number of the servers 28 stacked in layer on theserver rack 26 and the like are only examples, and they are not limitedto the numbers in FIGS. 1 and 2. Further, as shown in FIG. 1, anevaporator 34 is provided at each of the servers 28 stored in the serverrack 26. In FIG. 1, in order to make the relation of the server 28 andthe evaporator 34 understandable, it is shown with the server 28 insteadof the server rack 26.

As shown in FIG. 1, a cooling coil 36 is provided inside the evaporator34. A refrigerant liquid flowing in the cooling coil 36 evaporates dueto high-temperature air generating from the server 28, and thereby,takes vaporization heat from the periphery to be gasified. Thereby, theserver 28 itself and high-temperature air discharged from the server 28are cooled.

Meanwhile, a cooling tower 38 is provided on the roof of the building12, and a circulation line 40 in which the refrigerant naturallycirculates is formed between the cooling tower 38 and the aforementionedrespective evaporators 34. More specifically, spiral piping 41 in whichthe refrigerant flows is stored in the cooling tower 38, and asprinkling pipe 42 which sprinkles water to the spiral piping 41 isprovided above the spiral piping 41. Further, a fan 44 is provided abovethe sprinkling pipe 42, and outside air is taken in from a side surfaceopening of the cooling tower 38 and discharged from a top surfaceopening, whereby a counter current of the sprinkled water and theoutside air taken therein is formed, and thereby, the outside air iscooled so that the temperature becomes lower than the intake airtemperature.

The cooling coil 36 provided in the evaporator 34 and the spiral piping41 provided in the cooling tower 38 are connected by return piping 46(refrigerant gas piping) for returning the refrigerant gas which isgasified in the evaporator 34 to the cooling tower 38, and supply piping48 (refrigerant liquid piping) for supplying the refrigerant liquidwhich is liquefied by cooling and condensing the refrigerant gas in thecooling tower 38 to the evaporator 34.

The return piping 46 and the supply piping 48 branch out halfway, andpass through the underfloor chambers 22A and 22B on the first floor andthe second floor to be connected to the evaporators 34 of the servers 28placed in the server room 14A on the first floor and the evaporators 34of the servers 28 placed in the server room 14B on the second floor. Insuch a constitution, by a rapid increase in the heat generation amountfrom the servers 28 in recent years, high-temperature heat generated(discharged) from the servers 28 is directly exchanged with therefrigerant flowing in the evaporators 34 as the heat is in thehigh-temperature state to promote evaporation of the refrigerant gas,and thereby transport power for transporting the vaporized refrigerantgas to the cooling tower 38 placed at a higher place than the evaporator34 can be obtained. As the refrigerant for use, chlorofluorocarbon, orHFC (hydrofluorocarbon) as an alternative CFC and the like can be used.Further, when used at a pressure lower than the atmospheric pressure,water can be used. Here, expression of the refrigerant includes bothrefrigerant gas in a gaseous state, and a refrigerant liquid in a liquidstate, and in FIG. 1, the flow direction of the refrigerant gas is shownby the white arrow, and the flow direction of the refrigerant liquid isshown by the black arrow.

Thereby, the circulation line 40 for naturally circulating therefrigerant is formed between the evaporator 34 and the cooling tower38. More specifically, a heat pipe with no power in which therefrigerant is sealed is constructed by the evaporator 34, the coolingtower 38 and the circulation line 40. Further, since the heat generationamount from the server 28 becomes large and refrigerant gas at a hightemperature can be formed, the cooling temperature for condensing therefrigerant gas can be set to be high, and the refrigerant gas can becondensed with the cooling capacity by the cooling tower 38. Thecondensed refrigerant liquid flows down to the evaporator 34 locatedbelow the cooling tower 38.

Further, each of the evaporators 34 is provided with a temperaturesensor 50 which measures the temperature of the air after thehigh-temperature air discharged from the server 28 is cooled with theevaporator 34, and a valve 52 (flow regulating device) for regulatingthe supply flow rate (refrigerant flow rate) of the refrigerant which issupplied to the cooling coil 36 is provided at an outlet port of thecooling coil 36. A controller not illustrated automatically regulatesthe opening degree of the valve 52 based on the measured temperature bythe temperature sensor 50. Thereby, when the temperature of the airafter cooled in the evaporator 34 becomes excessively lower than the settemperature, the opening degree of the valve 52 is reduced and thesupply flow rate of the refrigerant is reduced. By controlling thesupply flow rate of the refrigerant not to increase to be more thannecessary like this, the cooling load for cooling the refrigerant can bemade small, and therefore, sufficient cooling capacity can be exhibitedwith only cooling in the cooling tower 38.

Describing this in more detail, in the servers 28, the air in the serverrooms 14A and 14B is taken into the servers by the fans 30, and the airis heated. Heat exchange is performed between the heatedhigh-temperature air and the evaporators 34, and the temperature of thecooled air is measured by the temperature sensors 50.

Meanwhile, in the refrigerant natural circulation system, the condensingtemperature which is lower than the vaporization (evaporation)temperature is required, unlike the conventional compression typeair-conditioning system. Therefore, if the vaporization temperature canbe set to be high, the condensing temperature, namely, the temperatureof the outside air used in the cooling tower 38 can be made high, andthe cooling capacity in the cooling tower 38 can be used under theoutside air condition at a higher temperature. More specifically, in theintermediate seasons (spring season and autumn season) in which theoutside air temperature is relatively high, cooling with only thecooling tower is also made possible, and running cost can be reduced bysuppressing the operation of a refrigerator 68.

Further, on the roof of the building 12, a heat exchanger 54 havingcooling capacity larger than the cooling tower 38 is installed inaddition to the cooling tower 38, and the heat exchanger 54 is providedin a parallel line 64 branched from the circulation line 40. Morespecifically, as shown in FIG. 1, parallel return piping 58 and parallelsupply piping 60 which are branched from the return piping 46 and thesupply piping 48 respectively are connected to a secondary side coil 62of the heat exchanger 54. Thereby, the heat exchanger 54 is disposed tohave parallel relation in the flow of the refrigerant with respect tothe cooling tower 38.

Further, a primary side coil 66 of the heat exchanger 54 is connected tocooling water supply piping 70 and cooling water return piping 72 fromthe refrigerator 68, and the cooling water supply piping 70 is providedwith a delivery pump 74. Thereby, the cooling water (primaryrefrigerant) produced in the refrigerator 68 exchanges heat with therefrigerant (secondary refrigerant) in the heat exchanger 54, and coolsthe refrigerant. The working electric power for the refrigerator 68 canbe reduced by connecting the refrigerator 68 to a cooling tower 76different from the above described cooling tower 38 and using it as acold heat source of the refrigerator 68. The structure of the coolingtower 76 is the same as that of the above described cooling tower 38.

The parallel return piping 58 is provided with a parallel valve 59, ashut-off valve 61 is provided in the vicinity of the cooling tower 38 inthe supply line 48, and the cooling water supply piping 70 in whichcooling water flows is also provided with a valve 69. Meanwhile, anoutside air temperature sensor 63 which measures the outside airtemperature is provided in the vicinity of the cooling tower 38, andtemperature sensors 65 and 67 are provided at a cooling tower outletport (refrigerant liquid side) and a heat exchanger outlet port(refrigerant liquid side). The measurement results of the respectivetemperature sensors 63, 65 and 67 are sequentially input in a parallelcontrol part 71, and the parallel control part 71 controls therespective valves 59, 61 and 69 based on the measurement result.Thereby, the parallel control mechanism is formed. The temperaturesensors 65 and 67 are provided at the cooling tower outlet port and theheat exchanger outlet port, but pressure sensors (not illustrated) whichmeasure the pressure of the refrigerant flowing in the piping can beprovided, and both the liquid temperature sensors 65 and 67 and thepressure sensors may be provided.

Here, a preferable mode of a control method by the parallel controlmechanism will be described.

In the first control method, the parallel control part 71 calculates thecapacity to cool the refrigerant in the cooling tower 38 from themeasurement result of the outside temperature sensor 63, and regulatesthe opening degree amount of the parallel valve 59 from the calculationresult, whereby the parallel control part 71 controls the refrigerantamount to be fed to the heat exchanger 54. Thereby, the cooling tower 38and the heat exchanger 54 can be efficiently used so that the runningcost becomes the minimum in accordance with the cooling load necessaryfor condensing the refrigerant gas vaporized in the evaporator 34.

The cooling capacity of the cooling tower 38 significantly depends onthe outside air temperature, and therefore, by conducting the control asdescribed above, a part of the refrigerant flowing in the circulationline 40 can be caused to flow into the heat exchanger 54 automaticallyin accordance with the variation in the outside air temperature.Therefore, only insufficiency of the cooling capacity of the coolingtower 38 needs to be supplied by the heat exchanger 54. Thereby, therunning cost can be further reduced.

Further, in the second control method, the parallel control part 71regulates the opening degree amount of the parallel valve 59 so that themeasurement result of the temperature sensor 65 at the outlet port ofthe cooling tower becomes a predetermined value and controls therefrigerant amount to be fed to the heat exchanger 54. Thereby, bymeasuring the refrigerant temperature at the outlet port of the coolingtower, the cooling capacity which the cooling tower 38 has at the pointof time of measurement can be grasped. Accordingly, a part of therefrigerant flowing in the circulation line 40 can be automaticallycaused to flow in the heat exchanger 54 by automatically regulating theopening degree amount of the parallel valve 59 based on the measurementresult, and therefore, only insufficiency of the cooling capacity of thecooling tower 38 needs to be supplied by the heat exchanger 54. Thereby,the running cost can be further reduced.

Further, when these control methods are carried out, the temperaturesensor 67 provided at the outlet port of the heat exchanger is measured,and thereby, the temperature of the refrigerant to be supplied to theevaporators 34 can be known. Accordingly, by controlling the openingdegree amount of the valve 69 of the cooling water supply piping 70based on the measurement result, the refrigerant can be prevented frombeing cooled more than necessary in the heat exchanger 54. Further, inthe summer season when the cooling capacity of the cooling tower 38reduces the most, combined use of the cooling tower 38 and the heatexchanger 54 sometimes becomes a disadvantage from the viewpoint of therunning cost. Thus, in such a case, by closing the shut-off valve 61when the measurement temperature of the outside temperature sensor 63reaches a predetermined value or higher, the running cost can be furtherreduced.

The two cooling devices that are the cooling tower 38 and the heatexchangers 54 are included, and each of them bears each share of worklike this. Thereby, stable operation of the cooling system can beguaranteed, and the running cost for cooling the refrigerant can bereduced.

Second Embodiment

FIG. 3 is a conceptual view showing a cooling system 100 for anelectronic device of a second embodiment of the present invention. Thesame members and constitutions as those in the first embodiment will beomitted.

In the cooling system 100 of the second embodiment, an air-conditioningmachine 78 for cooling server rooms 14A and 14B is provided in theconstitution of the cooling system 10 of the first embodiment, and therefrigerant of the circulation line 40 is used as a cold heat source ofthe air-conditioning machine 78.

More specifically, as shown in FIG. 3, machine rooms 80A and 80B arerespectively provided adjacently to the server rooms 14A and 14B, andthe air-conditioning machines 78 are installed in the machine rooms 80Aand 80B, respectively. Further, inlet ducts 79 which take the air of theserver rooms 14A and 14B into the air-conditioning machine 78 via themachine rooms 80A and 80B are placed by being penetrated throughpartition walls 82 which partition the server rooms 14A and 14B and themachine rooms 80A and 80B, and one end of the inlet duct 79 is connectedto a cooling part 84 of the air-conditioning machine 78. Further, oneend of an outlet duct 81 is connected to an air blower 86 of theair-conditioning machine, and the other end is extensively provided ineach of underfloor chambers 22A and 22B through the partition wall 82.Thereby, the air taken into each of the air-conditioning machines 78 viaeach of the intake ducts 79 is cooled by each of the cooling parts 84 ofeach of the air-conditioning machines 78, and blown into each of theunderfloor chambers 22A and 22B via each of the outlet ducts 81 by eachof the air blowers 86. Subsequently, the air is blown out to each of theserver rooms 14A and 14B from floor surfaces 20A and 20B. In this case,the air outlets (not illustrated) of the floor surfaces 20A and 20B arepreferably formed so that cooling air is blown to the vicinity of thefront surface of the server 28. The front surface of the server 28 meansthe opposite side of the evaporator 34.

Further, the cooling part 84 of the air-conditioning machine 78 isconnected to an air-conditioning circulation line 88 branched from thecirculation line 40. More specifically, air-conditioning supply piping88A and air-conditioning return piping 88B which constitute theair-conditioning circulation line 88 are connected to the cooling part84 of the air-conditioning machine 78.

According to the cooling system of the second embodiment constituted asdescribed above, the following effect can be exhibited in addition tothe effect of the above described first embodiment.

More specifically, the refrigerant of the circulation line 40 of whichrunning cost for cooling the refrigerant is low is used as the cold heatsource of the air-conditioning machine 78 for cooling the server rooms14A and 14B with cold air. Thereby, the running cost for operating theair-conditioning machine 78 also can be reduced. Further, by using theair-conditioning machine 78 and the evaporator 34 for cooling the server28 in combination, generation of heat accumulation (localhigh-temperature regions) in the server rooms 14A and 14B can besuppressed, and the supply air temperature from the air-conditioningmachine 78 which air-conditions the entire server room can be raised, ascompared with the conventional air-conditioning system (the method forair-conditioning by circulating air in the entire electronic equipmentroom by air-conditioning with the air blown from the floor shown inJapanese Patent Application Laid-Open No. 2004-232927). Thereby, in thepresent invention, vaporization (evaporation) temperature of therefrigerant can be made high as compared with the conventional system,and the capacity of the cooling tower 38 can be sufficiently used.

Accordingly, supplying the refrigerant of the circulation line 40 to thecooling part 84 of the air-conditioning machine 78 contributes to bothenergy saving of the air-conditioning machine 78 and exhibition of thecapacity of the cooling tower 38.

Third Embodiment

FIG. 4 is a conceptual view showing a cooling system 200 for an electricdevice of a third embodiment of the present invention. Explanation ofthe same members and constitutions as those in the second embodimentwill be omitted.

The cooling system 200 of the third embodiment has the constitution inwhich a plurality of servers 28 equipped with the evaporators 34 aredivided into groups, and thereby, the cooling system 200 can be operatedwith the groups being edge-cut from each other, in addition to theconstitution oft he cooling system 100 of the second embodiment.

More specifically, as shown in FIG. 4, a plurality of the servers 28equipped with the evaporators 34 are divided into a plurality of groups.In the case of FIG. 4, the servers 28 installed in the server room 14Aon the first floor are grouped as one group, and the servers 28installed in the server room 14B on the second floor are grouped asanother group. The method for grouping is not limited to the abovedescription, and the servers 28 can be further divided into smallgroups.

Two of heat exchangers 90 for groups, which is the number of groups intowhich the servers 28 are divided, are provided halfway in thecirculation line 40, and the circulation line 40 is constituted of amain circulation line 40A in which the refrigerant circulates betweenthe cooling tower 38 and/or the heat exchanger 54, and the heatexchanger 90 for a group, and a group circulation line 40B in which therefrigerant circulates between the heat exchanger 90 for a group and theevaporator 34.

Further, in the second embodiment, as the cold heat source of theair-conditioning machine 78, the refrigerant flowing in the circulationline 40 is directly supplied to the cooling part 84 of theair-conditioning machine 78, but in the third embodiment, theair-conditioning machines 78 are divided into two groups of theair-conditioning machine 78 installed in the machine room 80A on thefirst floor, and the air-conditioning machine 78 installed in themachine room 80B on the second floor. The group circulation lines 40Bcorresponding to the groups are connected to the cooling parts 84 of therespective air-conditioning machines 78.

According to the cooling system 200 of the third embodiment constitutedas described above, the following effect can be exhibited in addition tothe effect of the second embodiment described above.

More specifically, if abnormality occurs to, for example, the evaporator34 of one group, or the flow of the refrigerant stops, the abnormalitydoes not affect the other group. Accordingly, occurrence of abnormalityto cooling of all the servers 28 placed in the server rooms 14A and 14Bcan be prevented. Further, by also grouping the air-conditioningmachines 78, even if abnormality such as stoppage of the flow of therefrigerant occurs in one group, the abnormality does not affect thecooling parts 84 of the air-conditioning machines 78 of the other group.

Fourth Embodiment

FIG. 5 is a conceptual view of a cooling system 300 for an electronicdevice of a fourth embodiment of the present invention, and is a viewmade by changing FIG. 1 so that the cooling tower 38 and the heatexchanger 54 are in series positional relation. As in the firstembodiment, the case in which the cooling tower 38 and the heatexchanger 54 are installed so as to be in parallel positional relationis described, the redundant parts are omitted, and the same members andconstitutions are described by being assigned with the same referencenumerals and characters.

As shown in FIG. 5, the refrigerant gas which is vaporized in theevaporator 34 reaches the cooling tower 38 via the return piping 46 ofthe circulation line 40, where the refrigerant is cooled and becomes arefrigerant liquid, and thereafter, the refrigerant flows into the heatexchanger 54 via return piping 75 of a series line 73. In the heatexchanger 54, the refrigerant liquid further cooled by heat exchangewith the primary refrigerant (cooling water) flows into the supplypiping 48 of the circulation line 40 via outward piping 77 of the seriesline 73. Thereby, the heat exchanger 54 is disposed in the seriesrelation with respect to the cooling tower 38 in the flow of therefrigerant.

Further, a valve 69 and a regulating valve 87 are provided in thecooling water supply piping 70 and the cooling tower outlet port, theoutside air temperature sensor 63 is provided near the cooling tower 38,and the temperature sensors 65 and 67 are provided at the cooling toweroutlet port and the heat exchanger outlet port, respectively. Further, abypass line 83 which can pass the refrigerant gas returning from theevaporator 34 into the heat exchanger 54 is provided, and a bypass valve85 is provided in the bypass line 83. In order to distinguish the bypassline 83 and the series line described above, the bypass line 83 iswritten to be in a wavy shape in FIG. 5. The measurement results of therespective temperature sensors 63, 65 and 67 are input in a seriescontrol part 89, and the series control part 89 controls the respectivevalves 69, 85 and 87 based on the measurement results. Thereby, theseries control mechanism is formed. In FIG. 5, the temperature sensors65 and 67 are disposed at the cooling tower outlet port and the heatexchanger outlet port respectively, but the pressure sensor whichmeasures the pressure of the refrigerant flowing in the piping can beprovided, and both the temperature sensors and the pressure sensors maybe provided.

Here, a preferable mode of a control method according to the seriescontrol mechanism will be described.

Though the cooling load on the heat exchanger 54 becomes large in thesummer season when the cooling capacity of the cooling tower 38 reduces,the series control part 89 conducts control so that the measurementresult at the heat exchanger outlet sensor becomes a predeterminedvalue, and thereby, the series control part 89 can control the heatamount of the primary refrigerant so that only insufficiency of thecooling capacity of the cooling tower 38 is supplied in the heatexchanger 54 when the refrigerant sequentially flows into the heatexchanger 54 from the cooling tower 38. Accordingly, unnecessary coolingenergy is not required in the heat exchanger 54.

Further, the cooling capacity of the cooling tower 38 varies dependingon the outside air temperature, and therefore, when the refrigerantamount flowing in the spiral piping 41 in the cooling tower 38 is toolarge in the summer season and intermediate season, the refrigerantsometimes cannot be cooled to the temperature required for naturallycirculating the refrigerant. Accordingly, the refrigerant gas flow rateto the cooling tower 38 is controlled by operating the opening degreesof the bypass valve 85 provided in the bypass line and the regulatingvalve 87 provided in the outlet port of the cooling tower so that themeasurement result of the temperature sensor 65 at the outlet port ofthe cooling tower is controlled to be a predetermined value. Thereby,the temperature of the outside air which is the cold heat source of thecooling tower 38 can be effectively used irrespective of a summerseason, intermediate seasons or a winter season, and therefore, therunning cost can be further reduced.

Here, the predetermined value refers to the temperature or pressurerequired for naturally circulating the refrigerant in the circulationline.

Thus, in the fourth embodiment of the invention of the presentapplication, even when the cooling tower 38 and the heat exchanger 54are disposed in series, only the insufficiency of cooling of the coolingtower 38 has to be supplied in the heat exchanger 54 by firstly coolingthe refrigerant gas returning from the evaporator 34 in the coolingtower 38, and then passing the refrigerant through the heat exchanger54, and cold heat of outside air can be effectively used in the coolingtower 38 throughout a year.

As a more preferable mode of the series control mechanism, the seriescontrol part 89 fully closes the regulating valve 87 and fully opens thebypass valve 85 so as to shut off the return of the refrigerant gas tothe cooling tower 38 from the evaporator 34 and guide all therefrigerant gas to the heat exchanger 54, when the measurement result ofthe outside air temperature sensor 63 reaches a predetermined value ormore in a summer season. Thereby, the running cost in the summer seasoncan be further reduced.

The above described second embodiment or third embodiment can becombined with the constitution of the fourth embodiment in which thecooling tower 38 and the heat exchanger 54 are disposed in series.

SUMMARY OF THE PRESENT INVENTION

According to the cooling system for an electronic device of the presentinvention, an electronic device required to perform a precise operationwith an amount of heat generation from itself being large, such as acomputer and a server, can be efficiently cooled at low running cost.

-   (A) By adopting the refrigerant natural circulation method, and    using the difference of elevation of the disposed positions and the    treatment temperature difference between the evaporator 34 and the    cooling tower 38, transfer power for the refrigerant (heat) is not    needed. In the refrigerant natural circulation method, when a    difference ΔT between the temperature of the air which is discharged    from the evaporator 34, and is measured by the temperature sensor    50, and the air temperature at which the refrigerant is cooled in    the cooling tower 38 is 5° C. or higher, the system operates, and    the refrigerant can be transferred without power. In the cooling    system of the conventional central air-conditioning method, about    10% of the total power required by the system is occupied by the    pump power which transfers the refrigerant, and the pump power    required for the refrigerant transfer (also called heat transfer)    can be reduced.

Further, as a result that the heat generation amount from the server 28in recent years has abruptly increased, and heat at a high temperature(high-temperature air) generates from the server 28, the above describedΔT increases more than ever. Thus, with increase in the ΔT, the heattransfer amount (heat treatment amount of the system) increases. Theheat transfer amount changes in accordance with the specifications ofthe heat exchanger 54, but with ΔT=15° C., cooling of about a half ofthe server heat generation amount (with ΔT=30° C., the total heatgeneration amount of the server) is possible (when the server heatgeneration is 15 kW, heat treatment of 7.5 kW with ΔT=15° C. ispossible, and heat treatment of all of 15 kW is possible with ΔT=30°C.). The server rack exhaust (air temperature at the side of theevaporator) is normally at about 40° C. When the outside air temperatureis 25° C. (corresponding to ΔT=15° C.) or lower, a half of the serverheat generation can be cooled with only the outside air, and when theoutside air temperature is 10° (corresponding to ΔT=30° C.) or lower,the total amount of the server heat generation can be treated with theoutside air. For example, the number of hours when the outside airtemperature is 10° C. or lower is about 2600 hours (about 30% of thetotal number of hours) in Tokyo, and if the operation using the outsideair cold heat is performed only when at the outside air temperature of10° C. or lower, the heat load on the heat source can be reduced morethan the conventional systems by 30%. Further, the number of hours whenthe outside air temperature is 10° C. to 25° C. is about 40% of thetotal number of hours, and if 50% of the total server heat generation istreated with the outside air by also using the outside air during thisseason (intermediate seasons), the heat load of the heat source can bereduced more than the conventional systems by 50%.

-   (B) By adopting the cooling tower 38 for cooling the refrigerant    gas, and effectively using cold heat which low-temperature outside    air in a winter season and intermediate seasons (spring and autumn)    has, the cooling heat amount which is produced by the heat source    facility (in the conventional system, the compressor of a package    air conditioner) can be reduced. In fact, the efficiency of the    conventional package air conditioner: COP [cold heat amount to be    produced (kW)/Input power amount (kW)] is 2 to 2.5, but COP is 30 or    more in the cooling by using outside air of the present invention.-   (C) By locally cooling each server 28 by using the evaporator 34    close to the server 28, local heat accumulation can be prevented.

For example, in a data processing center facility, the air temperatureconditions under which the server mounted on the server rack normallyoperates are specified, and intake air condition is generally 25° C. orlower though it depends on the server.

Meanwhile, the conventional air conditioning of a method of blowing airfrom the floor is operated with the temperature of the supply air fromthe package air-conditioning machine at about 18° C., and thetemperature of the return air to the air-conditioning machine at about26° C. This is because in the actual operation, server rack exhaust air(normally at about 40° C.) and supply air are partially mixed and aretaken into the server rack, and therefore, in order to satisfy theserver rack intake air temperature of 25° C., the supply air temperaturehas to be low (actual air temperature is about 18° C.).

In contrast to this, when the server rack is cooled with the local heattreatment unit method, the outlet port air temperature of 25° C. issatisfied. Therefore, even if the supply air temperature is not low,namely, is higher than 18° C., the server intake air temperature of 25°C. can be satisfied, and when, for example, the supply air temperatureof 23° C. and the conventional temperature of 18° C. are compared, thetemperature can be increased by 5° C. Generally, in the cooling systemof the package air-conditioning method, the above described efficiency(COP) can be increased by about 3% by increasing the supply airtemperature by 1° C., and by increase of the supply air temperature by5° C., the COP can be increased by about 15%.

For prevention of heat accumulation by such local cooling, the influenceof the heat accumulation on an electronic device such as the server 28is conventionally prevented by reducing the temperature of theair-conditioning air which is supplied to the server rooms 14A and 14Bfrom the air-conditioning machine 78. However, when the supply airtemperature is reduced like this, the temperature of the refrigerant gaswhich is vaporized in the evaporator 34 becomes too low. As a result,the set temperature of the refrigerant device which cools and condensesthe refrigerant gas has to be made low, and the cooling device having acooling capacity which is not so large, such as the cooling tower 38cannot be used.

In contrast to this, in the present invention, by supplying therefrigerant which is cooled in the cooling tower 38 to the cooling part84 of the air-conditioning machine 78, the supply air temperature can beprevented from becoming too low, and therefore, the cooling devicehaving a cooling capacity which is not so large, such as the coolingtower 38 can be used. Further, as a result that the supply airtemperature can be increased, the COP of the entire cooling system canbe increased. In this case, even with the constitution in which therefrigerant which is cooled in the cooling tower 38 is supplied to thecooling part 84 of the air-conditioning machine 78, heat accumulationcan be sufficiently prevented, and no problem arises.

Further, in the present invention, the cooling tower 38 is disposedabove the evaporator 34 to circulate the refrigerant naturally, but therefrigerant can be transferred with refrigerant pumps instead of beingnaturally circulated by providing the refrigerant pumps not illustratedin the supply piping 48 of the circulation line 40 and the branchedsupply piping 60, for example. Thereby, in the positional relation ofthe evaporator 34 and the cooling tower 38, the cooling tower 38 doesnot have to be disposed above the evaporator 34, and the evaporator 34and the cooling tower 38 can be freely disposed without limitation onthe disposition of the evaporator 34 and the cooling tower 38.

The cooling systems 10, 100 and 200 in the above described first tothird embodiments are described with the example of the server 26 as anelectronic device, but the present invention can be applied to allelectronic devices which are required to perform precise operations withthe heat generation amount from itself being large.

1. A cooling system for an electronic device, comprising: an evaporator that cools exhaust air from the electronic device by vaporizing a refrigerant with heat generated from the electronic device; a cooling tower which is provided at a place higher than the evaporator, cools the refrigerant and condenses the vaporized refrigerant; a circulation line in which the refrigerant naturally circulates between the evaporator and the cooling tower a heat exchanger which exchanges refrigerant heat with water heat so as to cool the refrigerant, wherein the refrigerant flows in a first piping of the heat exchanger and the water flows in a second piping of the heat exchanger; a parallel line connected to the circulation line, the parallel line being a flow path for the refrigerant and producing a parallel relationship between the heat exchanger and the cooling tower; a temperature sensor which is provided at an outlet of the first piping of the heat exchanger; a valve which is provided in the second piping; and a control device which controls the valve of the second piping based on a temperature measured by the temperature sensor. 